The invention is concerned with herbicidal arylsulfonamide derivatives of phenoxybenzoic acids.
The compound, 5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-nitrobenzoic acid, including the salt forms thereof, is known to have herbicidal activity. According to a particular herbicidal treatment, it has been proposed to apply this compound in a post-emergence fashion to control weeds, especially broadleaf weeds, in soybean fields. Accordingly, in such an application, a herbicide must possess the following two properties at the applied dosage rate: (1) the ability to control the target weeds; and (2) the ability to remain safe to the soybeans.
In attempting to improve on the herbicidal properties of 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid and salts thereof, various derivatives of these compounds have been proposed including alkyl and cycloalkyl esters, alkylthio esters, phenyl ester, alkyl and dialkyl amido and benzyl chloride forms. U.S. Patents which describe such compounds and the like include U.S. Pat. Nos. 3,652,645; 3,784,635; 3,873,302; 3,983,168; 3,907,866; 3,798,276; 3,928,416; and 4,063,929. European Pat. No. 3416 to Imperial Chemical Industries Limited describes various alkylsulfonamide derivatives of phenoxybenzoic acids. For example, the simple methyl ester of the above-mentioned acid, i.e., methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate, has been proposed, and it has been discovered that this compound has even greater herbicidal activity than 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid with respect to various weeds, e.g., broadleaf weeds. However, it has also been discovered that methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate has a relatively large degree of post-emergence herbicidal activity with respect to crops such as soybeans.
Accordingly, there is a need in the art for compounds which have a desirable combination of herbicidal properties with respect to weed activity and crop safety.